US3783940A

US3783940A - Apparatus for plugging well bores with hardenable fluent substances

Info

Publication number: US3783940A
Application number: US00245421A
Authority: US
Inventors: H Urbanosky
Original assignee: Schlumberger Technology Corp
Current assignee: Schlumberger Technology Corp
Priority date: 1972-04-19
Filing date: 1972-04-19
Publication date: 1974-01-08
Anticipated expiration: 1991-01-08
Also published as: CA966065A

Abstract

As a preferred embodiment of the apparatus of the present invention disclosed herein, an expansible bag mounted around a first tubular body is operatively arranged to be expanded into engagement with a well bore wall by a hardenable fluent substance initially contained in a selectively-operable displacement assembly including a second tubular body suspended from a cable and releasably coupled to the first body. Biasing means are operatively arranged for imposing opposed axial forces against the ends of the expanded bag to securely anchor the tool until the fluent substance has solidified. The new and improved apparatus further includes a unique release mechanism which is capable of withstanding severe shocks and other forces which may be imposed on the apparatus to guard against the unexpected or premature uncoupling of the two tubular bodies as it is being moved into a well bore and operated. The release mechanism is, however, easily and positively released by the discharge of the fluent substance from the displacement assembly.

Description

United States Patent 1191 Urbanosky Jan. 8, 1974 APPARATUS FOR PLUGGING WELL Primary Examiner.1ames A. Leppink BORES WITH HARDENABLE FLUENT Attorney-Ernest R. Archambeau, Jr. et a1.

' SUBSTANCES [5 7] ABSTRACT As a preferred embodiment of the apparatus of the Inventor: Harold J. Urbanosky, Pearland,

Tex.

[73] Assigneez schlumberger Technology present invention disclosed herein, an expans ible bag Corporation, New York mounted around a first tubular body 1s operatlvely arranged to be expanded into engagement with a well Filed; 1"- 1 1972 bore wall by a hardenable fluent substance initially [211 App]. 245,421 contained in a selectively-operable displacement assembly including a second tubular body suspended from a cable and releasably coupled to the first body. [52] US. Cl. 166/181, 166/187 Biasing means are operatively arranged f imposing [51] Int. Cl E21b 33/127 Opposed axial forces against the ends f the expanded of Search bag to ecurely anchor the too] the fluent sub- 166/206, 214 stance has solidified. The new and improved apparatus further includes a unique release mechanism which is References Cited capable of withstanding se'vere shocks and other UNITED STATES PATENTS forces which may be imposed on the apparatus to 2,815,817 12/1957 Conrad 166/181 guard against the unexpected of premature uncou- 2,ss5,oo7 5 1959 Hoffer 166/181 P g the two tubular bodies as it is being moved 1,681,596 8/1928 Reichard 166/181 into a well bore and operated. The release mechanism 2,885,011 5/1959 Frost 166/181 is, however, easily and positively released by the dis- Anderson 611 3i. charge of the fluent ubstance from the displacement 2,726,848 12/1955 Montgomery et a1. assembly 3,429,595 2/1969 McGill 285/320 17 Claims, 7 Drawing Figures PATENTED 81974 3. 783 940 sum 1 or 3 F/Gl PATENTED 4 SHEET 3 (If 3 APPARATUS FOR PLUGGING WELL BORIES WITH HARDENABLE FLUENT SUBSTANCES In various well-completion operations it is often desired to place a fluid-tight barrier or plug at a desired location in a larger-diameter well casing below the lower end of a substantially-smaller well pipe or tubing string. Typically, so-called through-tubing bridge plugs such as those shown in U.S. Pat. No. 3,556,215, U.S. Pat. No. 3,578,079 and U.S. Pat. No. 3,578,083 as well as the patents mentioned-therein are employed for situations of this nature. As illustrated in those patents, these tools generally include a fluid-displacement device in an upper housing which is supported by a suspension cable and releasably-coupled to a depending body carrying an initially-collapsed expansible tubular bag. Once the tool has been lowered through the tubing string and is in the well bore below its lower end, the displacement device is operated to discharge a hardenable plastic or cementitious composition into the expansible bag so as to firmly expand the bag into sealing contact with the well bore walls. After the remainder of the hardenable substance has been deposited on top of the bag, the upper portion is uncoupled from the lower portion of the tool and returned to the surface. Thereafter, once the hardenable substance within and on top of the expanded bag has hardened, a fluidbypass passage through the lower portion of the tool is closed to prevent fluid or pressure communication between the well bore intervals above and below this barrier.

Although these well-completion tools have met with considerable commercial success, the problem of releasably coupling the upper and lower portions of these tools has not been satisfactorily solved heretofore. For example, those skilled in the art will appreciated that any well-completion tool must be capable of withstanding severe impacts and various adverse forces. As a result, any release mechanism employed for releasably coupling the two portions of these through-tubing bridge plugs together must be insensitive to sharp shocks and extreme accelerational forces to prevent the tool from being prematurely separated. On the other hand, these release mechanisms must also be capable of being selectively actuated with a minimum effort to be certain that the upper and lower portions of the tool can be separated from one another without moving the lower portion upwardly from the position where the expanded bag is intended to be placed.

Accordingly, it is an object of the present invention to provide new and improved well-completion apparatus for plugging a well bore with an initially-fluent sub stance and including upper and lower bodies which are releasably coupled together in such a manner that they can be reliably uncoupled only after the fluent substance has been placed in the well bore and with a minimum of effort.

This and other objects of the present invention are attained by providing upper I and lower tandemlydisposed bodies having a fluid chamber and a displacement piston adapted to displace a hardenable fluent substance from the chamber onto an extendible support carried on the lower body. Coupling means releasably intercouple the two bodies together and include a laterally-movable abutment on one of the bodies coengaged with a fixed abutment on the other body, and a latch member co-operatively arranged to be moved 2 by the piston from a first position retaining the abutments co-engaged under extreme shock loads and cable tension forces to a second position for reliably disengaging the movable abutment from the fixed abutment with a minimum of effort.

The novel features of the present invention are set forth with particularity in the appended claims. The invention, together with further objects and advantages thereof, may be best understood by way of the following description of exemplary apparatus employing the principles of the invention as illustrated in the accompanying drawing, in which:

FIG. 1 depicts a preferred embodiment of a wellcompletion tool arranged in accordance with the principles of the present invention as the tool is being lowered through a tubing string to a desired location in a well bore;

FIGS. 2A-2C are successive cross-sectional elevational views of the new and improved tool depicted in FIG. 1 illustrating the initial positions of the various el ements thereof before the tool has been actuated;

FIG. 3 is an enlarged view of a portion of the selectively-operated coupling means employed with the present invention; and

FIGS. 4 and 5 successively depict the tool shown in FIG. 1 as it is being operated to plug a selected well bore interval and after the upper tool portion has been separated from the lower portion.

Turning now to FIG. 1, a well-completion tool 10 incorporating the principles of the present invention and dependently supported by a suspension cable 11 is depicted as it is being lowered through a string of tubing 12 toward a selected position below the lower end of the tubing string within a larger-diameter well bore 13 which, in this instance, is cased as at 14. If desired, a typical casing collar locator 15 may be incorporated with the tool 10 for determining the depth at which the tool is to be halted.

In the preferred embodiment depicted, the new and improved well-completion tool 10 includes selectivelyoperable fluid-displacement means 16 arranged in an upper body 17 of the tool and carrying a supply of an initially-fluent hardenable material which, upon command from the surface, is displaced into extendible, wall-engaging support means such as an expansible tubular bag 18 which is carried on an elongated body 19 detachably coupled below the upper body and adapted for supporting the fluent substance until it hardens into a solidified mass. As will subsequently be explained in greater detail, the upper and

lower tool bodies

17 and 19 are releasably coupled together by selectively operable coupling means 26) cooperatively arranged for releasing the lower body in response to the operation of the displacement means 16. Biasing means 21 carried on the lower body 19 are arranged for selectively imposing opposed axial forces against the ends of the expanded bag 18 to anchor the tool 10 after the tubular bag has been filled with a sufficient quantity of the fluent substance to expand it outwardly into sealing engagement with the well casing 14. Following the operation of the displacement means 16 and the release of the

tool bodies

17 and 19, the upper body is returned to the surface by respooling the cable 11. Thereafter, once sufficient time has elapsed for the fluent substance to adequately harden for forming an impermeable transverse bridge or a barrier permanently plugging the well casing 14, time-controlled bypass control means 22 mounted on the lower end of the body 19 operate to permanently close a bypass passage 23 in the lower body which is temporarily left open for equalizing pressure differentials acting across the inflated bag 18 until the fluent substance supported thereby has hardened.

Turning now to FIGS. 2A-2C, a cross-sectioned elevational view is shown of the well-completion tool as it appears before the collapsed bag 18 carried thereon is expanded. As previously mentioned, the tool 10 carries a substantial volume of a hardenable substance 24 which, upon operation of the fluiddisplacement displacement means 16, is forcibly displaced into the tubular bag 18 to expand it outwardly into sealing engagement with the well casing 14. Accordingly, the upper body 17 of the tool 10 is arranged to provide an enlarged chamber 25 in its upper portion that is joined by an axial passage 26 to an enlargeddiameter longitudinal bore 27 extending substantially the full length of the body and terminating at its lower end. The upper portion of the lower body 19 is also enlarged and similarly provided with an enlargeddiameter longitudinal bore 28 which extends upwardly to the upper end of the body. The adjacent ends of the upper and

lower bodies

17 and 19 are complementally fitted together and fluidly sealed as at 29, with the two bodies being releasably coupled to one another by the coupling means 20 so that their

respective bores

27 and 28 together define a combined fluid chamber 30 of substantial volumetric capacity.

The fluid-displacement means 16 also include a piston 31 initially positioned in the fluid chamber 30 just above the upper surface of the fluent substance 24. In this manner, upon downward movement of the piston 31, the fluent substance 24 will be displaced from the fluid chamber 30 and into the expansible bag 18. By providing one or more lateral ports 32 in the upper body 17, well bore fluids will be admitted into the longitudinal bore 27 for maintaining the space above the piston 31 as well as the fluent substance 24 in the fluid chamber 30 at the hydrostatic pressure of the well bore fluids.

To move the displacement piston 31 downwardly, the fluid-displacement means 16 further include a cylindrical weight 33 initially disposed in the enlarged bore 27 immediately above the piston and releasably supported therein by two or more inwardly-movable upright latch fingers 34 arranged on the upper end of the weight. As illustrated in FIG. 2A, the latch fingers 34 have outwardly-enlarged heads 35 which are adapted to be received in an enlarged portion 36 of the axial passage 26 immediately above the upper end of the enlargeddiameter longitudinal bore 27 and defining a shoulder 37 to support the heads so long as the fingers are laterally separated. To retain the latch fingers 34 initially separated, an actuating piston 38 disposed in the chamber 25 carries a depending rod 39 which extends through the axial passage 26 into the enlarged recess 36 so as to be interposed between the opposed heads 35 of the fingers so long as the actuating piston is not further elevated by a compression spring 40 mounted within the chamber.

To retain the actuating piston 38 in its position depicted in FIG. 2A, the upper portion of the chamber 25 is initially filled by a relatively non-compressible fluid such as water or oil; and this hydraulic fluid is retained therein so long as a normally-closed solenoid valve 41 connected to electrical conductors 42 in the cable 11 is not operated to open communication by way of a fluid passage 43 between the chamber and the exterior of the tool 10. Accordingly, it will be appreciated that once the upper end of the chamber 25 has been filled with a sufficient volume of the hydraulic fluid to shift the actuating piston 38 downwardly to its illustrated position, the depending rod 39 will be positioned in the recess 36 between the opposed enlarged heads 35 for maintaining the weighted body 33 releasably suspended just above the displacement piston 31.

As seen in FIGS. 2A ans 3, in the preferred manner of arranging the selectively-operable coupling means 20, the lower end of the upper body 17 is adapted to be complementally received within the upper end of the enlarged longitudinal bore 28 in the lower body 19. An inwardly-opening circumferential groove 44 is formed around the wall of the lower body 19 for defining a fixed downwardly-facing inclined abutment, as at 45, adapted for engagement with generallycomplemental oppositely-directed abutment surfaces, as at 46, on outwardly-enlarged

heads

47 and 48 respectively arranged on the lower ends of a pair of inwardly-

movable latch fingers

49 and 50 which are in turn dependently mounted from opposite sides of the lower end of the upper body 17. A transverselyoriented latch member 51 is pivotally coupled, as at 52, to the enlarged head47 of one of the fingers 49 and suitably dimensioned to engage the tip 53 of the latch member with the rear of the opposite enlarged head 48 so as to retain the enlarged heads within the circumferential groove 44 until the latch member is pivoted upwardly a sufficient distance to bring its tip into registration with an opening 54 in the opposite head. To selectively release the latch member 51 from its depicted horizontal or transverse position, an upstanding member 55 is mounted thereon and extended upwardly at a slight angle from the vertical into the lower end of the upper tool body 17. For reasons that will subsequently be explained in greater detail, the upper end of the upstanding member 55 is tapered, as at 56, for engagement with the complementally-shaped interior surface 57 ofa depending skirt 58 on the lower end of the pis ton member 31 when the displacement piston is carried to the lower end of the fluid chamber 30 and contacts the upstanding actuating member. The purposes of this cooperative arrangement will be better appreciated once the operation of the new and improved tool 10 is fully explained.

To initially retain the fluent substance 24 within the fluid chamber 30, the lower end of the longitudinal bore 28 is normally closed as shown in FIG. 2B by an annular valve member 59 that is slidably arranged and fluidly sealed, as at 60, within the lower end of the enlarged bore. To normally secure the valve member 59 in its depicted elevated position, a shear pin 61 is arranged to releasably secure the valve member to the lower body 19 until the fluid pressure of the fluent substance 24 has been increased sufficiently to break the shear pin and shift the valve member downwardly.

For reasons that will subsequently become apparent, an elongated tubular member 62 is coaxially supported as shown in FIGS. 2A and 28 within the bore 28 in the lower body 19 and terminated at its upper end by one or more lateral outlets 63 to provide communication between the upper end of the tubular member and the exterior of the tool 10. By providing an enlargeddiameter portion 64 on the tubular member 62 immediately adjacent to the normal elevated position of the valve member 59 and arranging a sealing member 65 thereon for engagement within the axial bore of the annular valve member, the fluent substance 24 thereabove cannot be displaced from the fluid chamber 30 until the valve member has moved downwardly a sufficient distance to bring its upper end below the sealing member 65.

The intermediate portion of the lower body 19 is sized to accommodate a pair of longitudinally-spaced

slidable collars

66 and 67 which are respectively fluidly sealed, as at 68 and 69, around the body and secured within the opposite ends of the tubular bag 18 which is preferably formed of a suitable wear-resistant, flexible and fluid-impervious material, such as a Dacron cloth impregnated with Neoprene, that does not readily stretch. The bag 18 is formed with an expanded diameter corresponding generally to that of the well casing 14, and is preferably foldedand lightly tied around the body 19 in this collapsed position. In its initiallycollapsed position illustrated in FIG. 2B, the tubular bag 18 is drawn to its full length with the

slidable collars

66 and 67 at their most-widely separated positions along the lower body 19; and the upper collar is releasably secured in its initial position by one or more upright latch fingers 70 which are inwardly biased to retain enlarged heads 71 thereon in a circumferential groove 72 around the body.

It will be noted that by virtue of the sealing

members

68 and 69 on the

slidable collars

66 and 67, the interior of the bag 18 defines an annular fluid-tight space around the body 19. Accordingly, to provide communication withinthe collapsed bag 13, one or more lateral ports 73 are arranged in the reduced-diameter portion of the body 19 at a location between the depicted elevated position of the upper collar 66 and the lower position to which the collar will slide downwardly in response to cable tension after the bag is initially expanded. The lower end of the elongated tubular member 62 is extended below the ports 73 and sealingly engaged, as at 74, within the longitudinal bore 75 through the reduced portion of the body 19. Thus, so long as the upper collar 66 is retained in its initial elevated position by the latch fingers 70, once the valve member 59 is shifted downwardly, the fluent substance 24 released from the fluid chamber 30 will be directed through the annular space between the body 19 and the lower portion of the tubular member 62 and discharged into the bag 18 by way of the lateral ports 73.

It will, of course, be appreciated that once the upper collar 66 has been carried downwardly (as will subsequently be described) a sufficient distance to position the sealing member 68 on the collar below the lateral ports 73, the fluent substance 24 confined in the interior space within the expanded bag 18 will be trapped therein. For reasons that will subsequently be explained, a second circumferential groove 76 is formed around the reduced-diameter portion of the body 19 just below the lateral ports 73 so that, once the collar 66 has shifted downwardly in relation to the ports, the enlarged heads 71 on the latch fingers 70 will engage this lower groove to prevent the upper collar from subsequently moving upwardly from its lower position.

The selectively-operable biasing means 21 are preferably arranged on the lower body 19 somewhat below the lower collar 67. As illustrated in FIGS. 23 and 2C,

the biasing means 21 include an annular member 77 which is slidably mounted around the reduced portion of the body 19 and adapted to be moved upwardly thereon by a stout compression spring 78 arranged between a body shoulder 79 and the slidable member. For reasons that will subsequently be explained, the spring 78 is initially retained in compression by one or more ball members 86 that are respectively arranged in lateral recesses 81 spaced around the annular member 77 and sized for partial reception in a circumferential groove 82 formed around the intermediate portion of the lower body 19. A sleeve member 83 is coaxially mounted around the annular member 77 and has its lower portion formed with an internal diameter appropriately sized in relation to the diameter of the walls and the depth of the circumferential groove 82 to prevent outward lateral movement of the balls from the groove so long as the ball-retainer sleeve remains in the elevated position illustratedin FIG. 2B.

To permit selective outward movement of the balls 80 from the circumferential groove 82, longitudinal slots 84 are arranged around the upper portion of the retainer sleeve 83. Thus, upon downward movement of the retainer sleeve 83 in relation to the annular member 77 to bring the slots 84 into registration with the several balls 80, the upwardly-directed force of the compression spring 78 will be effective for shifting the annular member upwardly in relation to the lower body 19 once the balls are shifted outwardly from the circumferential groove 82 and into the enlarged space provided by the elongated slots. In this manner, once the ball-retainer sleeve 83 is moved downwardly against the restraint of a relatively-weak compression spring 85 mounted between the retainer sleeve and around the annular member 77, the stout compression spring 78 will be freed for shifting the annular member upwardly against the lower collar 67. To provide for the actuation of the ball-retainer sleeve 83, the lower collar 67 is appropriately formed, as at 36, to engage an inwardly-turned lip 87 on the upper end of the ballretainer sleeve to shift it downwardly in relation to the annular member 77 for releasing the balls 80 from the circumferential body groove 82.

As previously mentioned, the normally-open bypass passage 23 is provided for reducing, if not altogether equalizing, pressure differentials existing across the expanded bag 18 as the fluent substance 24 therein is hardening. Accordingly, as shown in FIG. 2C, one or more lateral ports 88 are formed in the lower tool body 19 well below the depicted initial position of the lower collar 67. In this manner, the bypass passage 23 through the body 19 between the upper and

lower ports

63 and 88 is defined by the tubular member 62 and the intermediate portion of the longitudinal bore 75 below the lower end of the tubular member. To selectively close this bypass passage 23, the bypass control means 22 include a tubular valve member 89 which is operatively disposed within the longitudinal bore 75 for movement upwardly from an initial position immediately below the lateral ports 88 to a final elevated position (as defined by a downwardly-facing shoulder 90 in the longitudinal bore) where longitudinally-spaced

sealing members

91 and 92 on the valve member are spanning the ports and sealingly engaged with the body 19 above and below the ports. Thus, the bypass control means 22 initially provide fluid communication through the tubular member 62 and the

bypass ports

63 and 88 for accommodating well bore fluids moving past the well-completion tool 10 during the time that the fluent substance 24 is hardening within the expanded bag 18.

To close the valve member 89, an elongated tension spring 93 is anchored at its upper end by a transverse rod 94 (FIG. 28) to the body 19 and has its remaining portion extended downwardly through the longitudinal bore 75 (FIG. 2C). The spring 93 is terminated by a long straight portion 95 which is passed through the valve member 89 and releasably secured in an initiallystretched condition by a hook 96 coupled to a cord 97 that is releasably secured to a geared timer mechanism 98 enclosed in an enlarged oil-filled chamber 99 in the lowermost portion of the lower tool body 19. The rotational speed of the uppermost gear 100 in the timer mechanism 98 is regulated by a train of gears that is terminated by a paddle-like wheel 101 which is driven by the force of the spring 93 acting through the gear train. Thus, by releasably coupling the cord 97 to the shaft 102 carrying the upper gear 100 of the gear train and winding the cord therearound, the tension force of the spring 93 will be effective for slowly rotating this uppermost gear at a speed which, by virtue of the gear train, is regulated by the faster, but retarded, rotational speed of the rotating paddle member 101 in the oilfilled chamber 99.

Accordingly, once the cord 97 is wound around the shaft 102 and coupled to the hook 96 on the lower end of the spring 93, a preselected time interval will be provided before a transverse member, such as a washer 103, loosely mounted on the straight portion 95 of the spring is moved upwardly to shift the valve member 89 upwardly to close the ports 88. In other words, once the cord 97 is connected, the tension force of the spring 93 will begin slowly unwinding the cord from the shaft 102 so that, once the gear 100 has been rotated a sufficient number of revolutions to substantially unwrap the cord, the lower end of the cord will be released from the shaft and the spring will then contract to jerk the washer 103 upwardly for carrying the valve member 89 to its final port-closing position.

To prepare the new and improved well-completion tool 10 for operation, the fluid chamber above the weight-releasing piston 38 is filled with a sufficient volume of a hydraulic fluid to shift the piston against the spring 40 to a position where the depending rod 39 extends downwardly into the recess 36. The weighted body 33 is forced upwardly, compressing a coil spring 104 thereabove until the enlarged heads 35 of the latch fingers 34 are on opposite sides of the rod 39 and are supported on the shoulder 37 for retaining the weighted body 33 in its elevated position above the fluid-displacement piston 31. The lower end of the upper body 17 is complementally fitted into the upper end of the lower body 19 and the latch member 51 is properly positioned to retain the opposed

enlarged heads

47 and 48 in the internal circumferential groove 44. The upper valve member 59 is secured in its upper or closed poisition by the shear pin 61; and the enclosed fluid chamber is then filled with a suitable plastic or cementitious initially-fluent substance, as at 24, which will harden into a solid mass that preferably expands slightly as it fully hardens.

The annular member 77 is shifted into position on the intermediate portion of the tool body 19 so as to place the balls 80 in the groove 82 and releasably retain the compression spring 78 in a compressed condition. The tension spring 93 is extended and connected by the hook 96 to the release cord 97 which has been wrapped around the gear shaft 102. As previously mentioned, the delay provided by the timer mechanism 98 before the bypass passage 23 is closed is governed by the number of turns or wraps of the cord 97 around the shaft 102. This time interval is, of course, selected so that the valve member 89 will not be actuated until some time later which is calculated to be sufficient to permit the initially-fluent substance 24 to have at least substantially hardened.

The tool 10 is then lowered into the well bore 13 by means of the suspension cable 11. Once the wellcompletion tool 10 has emerged from the lower end of the tubing string 12 and has reached a selected position therebelow, an electrical signal is sent through the cable conductors 42 to actuate the solenoid valve 41. As previously explained, once the solenoid valve 41 is opened, the hydraulic fluid within the upper chamber 25 will be discharged through the now-opened passage 43 as the compression spring 40 shifts the weightreleasing piston 38 upwardly. Once the weightreleasing piston 38 has reached a sufficiently-elevated position to withdraw the depending rod 39 from between the opposed ends 35 of the latch fingers 34, the weighted body 33 will be released.

Once the weighted body 33 is released, the force of the compressed spring 104 is effective for accelerating the weighted body rapidly downwardly so that it strikes the fluid-displacement piston 31 with considerable impact. In this manner, a substantial shock or pressure wave is developed in the fluent substance 24 which is effective for shifting the annular valve member 59 downwardly with sufficient force to break the shear pin 61. Once the shear pin 61 has failed, the upper valve member 59 will be moved downwardly a sufficient distance to bring its upper end below the seal 65 on the enlarged-diameter portion 64 of the axial tubular member 62 to open communication between the fluid chamber 30 and the filling ports 73 by way of the annular space between the axial tubular member and the inner wall of the intermediate portion of the lower body 19. A sealing member 105 is arranged on the lower end of the valve member 59 for sealing engagement with the lowermost portion of the enlarged bore 28 to prevent loss of the fluent substance 24 through a pressureequalizing port 106 provided in the enlarged bore below the upper sealing member 60.

Once the weighted body 33 has come to rest on top of the fluid-displacement piston 31, the weight of this body will be effective for moving the piston on downwardly through the fluid chamber 30 to forcibly displace a portion, as at 107, of the fluent substance 24 through the filling ports 73 and into the expansible bag 18. It will, of course, be appreciated that since the fluent substance 24 is initially at the hydrostatic pressure of the well bore fluids, the pressure developed by the weighted body 33 will be in addition to the hydrostatic pressure. Thus, as the bag 18 is filling, the increased fluid pressure developed in the fluent substance 24 by the weighted body 33 acting on the displacement piston 31 will be effective for expanding the bag outwardly with the enclosed portion 107 of the material and into contact with the walls of the well casing 14 immediately adjacent thereto. Expansion of the tubular bag 18 will, of course, be effective for drawing the unrestrained lower slidable collar 67 upwardly along the intermediate portion of the body 19 toward the still-latched upper collar 66. lt should be noted that the latch fingers 70 are stiff enough that the expansion of the bag 18 will draw the lower collar 67 upwardly without releasing the enlarged heads 71 from the upper circumferential groove 72.

Accordingly, when the expansible bag 18 is fully expanded, it will initially be in a position in which its opposite ends substantially assume a generallyhemispherical configuration instead of the toroidal configuration shown in FIG. 4. At this point, there will still be a substantial volume of the still-fluent substance 24 remaining in the fluid chamber 31} so that the increased fluid pressure developed in the interior of the bag 18 by the weight of the body 33 acting on the piston 31 will expand the bag outwardly against the well casing 14 with a moderate lateral force. Once the bag 18 is fully expanded, the discharge flow of the fluent substance 24 from the fluid chamber 30 will, of course, temporarily cease and the displacement piston 31 and the weighted body 33 will come to rest at the upper fluid level of the fluent substance still remaining in the fluid chamber.

It will be recognized that the fluid pressure expanding the bag 18 outwardly will urge the exterior of the bag against the well casing 14 with a lateral force that is effective to frictionally secure the bag against longitudinal movement. Therefore, upon upward movement of the suspension cable 11, the upper body 17 and the lower body 19 will initially be moved upwardly in relation to the stationary expanded bag 18 and the upper and lower

slidable collars

66 and 67. As will subsequently be explained in detail, this upward movement is effective for consecutively blocking further communication to the interior space in the expanded bag 18, actuating the biasing means 21, and ultimately freeing the upper tool body 17 from the lower tool body 19.

First of all, upon upward movement of the lower body 19, the inwardly-enlarged ends 71 of the latch fingers 74) will be cammed outwardly by the lower surface of the upper circumferential groove 72 to release the upper collar 66 for sliding movement in relation to the tool body. Thus, the continued upward movement of the lower body 19 will be effective for carrying the fill ports 73 above the stationary upper collar 66 and then bringing the lower circumferential groove 76 immediately below the fill ports up to or, perhaps, slightly above the heads 71 of the latch fingers 711. It will, of course, be recognized that once the lateral ports 73 pass above the fluid seal 68 on the upper collar 66, that portion 107 of the fluent substance 24 which has filled the expanded bag 18 will be sealingly enclosed therein. Moreover, once the lower circumferential groove 76 engages or passes above the latch fingers 70, the upper collar 66 cannot return upwardly in relation to the body 19 to a position where the ports 73 are again in communication with the interior space within the bag 18. Furthermore, as the lower body 19 is moved upwardly, the releasably-coupled annular member 77 will be carried upwardly toward the stationary lower collar 67 so as to bring the depending portion 86 thereof into contact with the inwardly-directed lip 87 of the ballretainer sleeve 83. Then, as the lower body 19 is moved further upwardly, the ball-retainer sleeve 83 will be halted and the continued movement of the annular member 77 will carry the balls 80 upwardly into registration with the elongated slots 84. As previously described, once the balls 80 move into registration with the elongated slots 84, they will be free to move outwardly into the enlarged space therearound to disengage the balls from the circumferential groove 82 around the intermediate portion of the body 19.

Accordingly, once the balls 80 are disengaged from the circumferential groove 82, the compressed biasing spring 78 will be released for forcibly urging the annular member 77 upwardly against the lower collar 67. Thus, as best seen in FIG. 4, once the compression spring 78 is released, it will impose a substantial upwardly-directed axial force against the lower end of the stationary expanded bag 18. The axial force will be effective for further increasing the fluid pressure of the still-fluent substance 107 trapped within the bag 18 which (if the enlarged heads 71 are below the groove 76) will initially move the upper collar 66 upwardly to accommodate the corresponding depression of the lower end of the bag. Once, however, the upper collar 66 reaches a position on the intermediate portion of the body 19 where the latch fingers are adjacent to the circumferential groove 76 just below the filling ports 73, the enlarged ends 71 thereof will be urged into the circumferential groove 76 to secure the upper collar from further upward movement. Once the upper collar 66 is secured against further movement in relation to the elongated body 19, the upwardly-directed axial force imposed on the lower end of the bag 18 by the stout compression spring 78 will be effective for developing a downwardly-directed opposing or axial reaction force on the upper end of the expanded bag for depressing the central portions of the upper and lower ends of the bag inwardly so that, ultimately, the expanded bag will assume the generally-toroidal configuration depicted in FIG. 4. The significance of this toroidal configuration is fully expained in US. Pat. No. 3,578,083 and, therefore, needs no further explanation.

Once the filling ports 73 are uncovered, the weighted body 33 will resume downward movement of the piston 31 to displace the remainder of the fluent substance 24 contained within the fluid chamber 30 into the well bore annulus defined between the casing 14 and that portion of the elongated body 19 projecting upwardly above the expanded bag 18. In this manner, the remainder of the fluent substance 24 will be deposited on top of the expanded bag 18, as at 108, to further assure that an impermeable plug or barrier of substantial vertical height will be formed in the well bore 13 once the two portions of the fluent substance, as at 107 and 168, have ultimately expanded and hardened.

As best seen in FIG. 3, as the piston 31 nears the end of its travel in the fluid chamber 30 (as defined by one or more inwardly-projecting stops 109 in the longitudinal bore 27), the lower edge of the piston skirt 58 will pass over the tapered end 56 of the upstanding member 55. It is, of course, readily apparent that the cooperative arrangement of the

complemental surfaces

56 and 57 will quickly tilt the upstanding member 55 toward a more-erect position which correspondingly pivots the latch member 51 upwardly from its depicted latching position for bringing the nose 53 of the latch member into registration with the hole 54 in the head 48. lnward movement of the opposed heads 47 and 48 will, of

course, secure the latch member 51 in its tool-releasing position as the latch tip 53 enters the hole 54.

As explained in U.S. Pat. No. 3,578,083, the perimeter of the bag 18 will be urged outwardly against the wall of the casing 14 with an increased anchoring force that is proportionally related to the total pressure of the still-fluent substance 107 confined within the expanded bag. Accordingly, as shown in FIG. 5, once the bag 18 is securely anchored in this manner, the upper body 17 of the tool is separated from the lower body 19 by simply pulling further on the suspension cable 11 so that the

heads

47 and 48 of the

latch fingers

49 and 50 will be released from the circumferential groove 44 at the upper end of the body once the displacement piston 31 has engaged the upstanding member 55 and shifted the latch 51 above the latch head 48. Then, at some predetermined time thereafter, the timer mechanism 98 will function to release the tension spring 93 so as to shift the valve member 89 upwardly across the lower bypass ports 88 and permanently close the bypass passage 23.

It will, of course, be appreciated that the several actions described above by reference to FlGS. 35 will occur successively once the solenoid valve 41 is opened and the cable 11 is pulled upwardly to close the filling ports 73 and reform the expanded bag 18 into its toroidal configuration. Thus, by simply maintaining a moderate strain on the cable 11, at the completion of the setting operation the release of the coupling means will occur and the two

bodies

17 and 19 will be sepa rated without further action.

As previously mentioned, the new and improved coupling means 20 employed with the completion tool 10 of the present invention are particularly arranged to re liably retain the upper and

lower tool bodies

17 and 19 latched to one another even when severe shocks are imposed thereon. On the other hand, in keeping with the objects of the present invention, it is also essential that the coupling means 20 be fully capable of dependable actuation to permit the upper body 17 to be easily separated from the lower body 19 even when there are increased frictional forces otherwise tending to retain the

enlarged heads

47 and 48 in the circumferential body groove 44 such as will occur under extreme tension loads on the suspnsion cable 11.

These two conditions i.e., resistance to shock and ease of release would, of course, ordinarily be considered to be contrary to one another. Thus, heretofore, the usual technique has been to attempt to reach a compromise where a typical release mechanism will hopefully withstand moderate shocks but still release with only a slightly-higher actuatingforce than is preferred. As is typical in most situations such as this, neither of the opposing conditions are fully satisfied; and, often as not, a tool malfunction will occur.

Accordingly, the new and improved coupling means 20 employed with the present invention are cooperatively arranged to meet both conditions. First of all, to assure that the

tool bodies

17 and 19 will be reliably released, it is preferred to employ only the two latch finmovement of the latch member. Thus, only a very slight downward force is required of the displacement piston 31 to assure the release of the

bodies

17 and 19.

As mentioned above, two frictional forces are involved in determining the ease with which the

bodies

17 and 19 can be separated. First of all, the relative inclination of the abutment surfaces 45 and 46 will govern the tension force which must be imposed on the cable 11 to operate the coupling means 20. For instance, if the abutment surfaces 45 and 46 are perpendicular with respect to the longitudinal axis of the

tool gers

49 and 50 to couple the bodies together. In this 10, all of the tension forces on the cable 11 would be directly applied to the abutment surfaces 45 and 46 along a longitudinal load axis and there would be no laterally-directed force tending to move the

latch fingers

49 and 50 inwardly so as to release the

bodies

17 and 19. Thus, the angle of inclination of the opposed abutment surfaces 45 and 46 must be selected so as to at least produce an inwardly-directed lateral force on the

latch fingers

49 and 50 in response to tension on the cable 11.

The other frictional force which will determine how readily the coupling means 20 will operate to release the

bodies

17 and 19 is the frictional force imposed between the rear surface of the latch finger 48 and the nose 53 of the latch member 51. It will, of course, be appreciated that this frictional force will be dependent upon the inclination of the abutment surfaces 45 and 46 since the resultant inwardly-directed lateral force acting on the nose 53 of the latch member 51 will be directly dependent on the angle of this inclination. Thus, as this angle increases, the frictional force tending to prevent upward pivotal movement of the latch member 51 will corerspondingly increase.

As a result, therefore, the angle of inclination of the abutment surfaces 45 and 46 is selected to assure inward movement of the

latch fingers

48 and 49 with a moderate cable tension but without imposing an extreme inwardly-directed lateral force on the latch member 51. Although there are, of course, many variables, it has been found that this angle of inclination a ll lll lfilll fifllfi tens o @P t from the horizontal, with 30 being the particular choice used in the preferred embodiment of the present invention. This choice is, however, not to be considered as a limitation on the scope of the present invention.

It would seem that by virtue of the ease with which the latch member 51 can be pivoted upwardly, the coupling means 20 would be highly sensitive to even moderate shock forces which would tend to inadvertently release the two

bodies

17 and 19. However, the coupling means 20 are cooperatively arranged to withstand substantial impacts and shocks. For instance, downward movement of the fluent substance 24 past the latch member 51 is totally incapable of releasing the latch member since the contact of the upper portion of the upstanding member 55 against the adjacent wall of the lower body 19 prevents downward pivotal movement of the latch member. Similarly, any downwardlyacting pressure surges (such as when the weighted body 33 is released) on the latch member 51 are incapable of tripping the latch member. The same protection is also provided even when the tool 10 strikes a projection as it is being lowered into the well bore 13 and is slowed or rapidly halted so as to impose downwardlyimposed inertial forces on the latch member 51.

Those skilled in the art will, of course, appreciate that should a sharp lateral force or shock be imposed on the right-hand side (as viewed in the drawings) of the lower tool body 19 or the tool be swung so as to impact its right-hand side against an object, the sensitively-arranged latch member 51 could possibly be pivoted upwardly by inertia. However, to counter this reaction, the mid-portion of the upstanding member 55 is substantially reduced, as at H10, for greatly minimizing the mass which would otherwise tend to pivot the latch member 51 upwardly (in a clockwise direction as viewed in FIG. 3) in response to these forces. Impacts or shocks acting in the reverse manner will, of course, simply tend to pivot the latch member 51 in the opposite direction and this will be prevented by the upstanding member 55 resting on the body 19. To further counter this unwanted reaction, a spring 111 is mounted on the latch member 51 adjacent to the pivot 52 so as to provide a counteracting biasing force about equal to the inertial force of the upstanding member 55. Thus, a lateral inertial force tending to shift the upstanding member 55 upwardly toward a more-erect position is opposed by the biasing action of the spring 111 urging the latch member 51 downwardly.

Accordingly, it will be appreciated that the new and improved completion tool 10 of the present invention is particularly arranged to reliably plug a well bore with a hardenable substance carried in the tool. By arranging the tool with upper and lower bodies which are releasably secured together by shock-resistant release means which are released only by the discharge of the fluent substance onto an extendible support on the lower body, the upper body can be easily separated from the lower body. Moreover, by virtue of the unique design of the shock-resistant release means, the risk that the tool bodies will be inadvertently uncoupled is substantially reduced without-impairing the sensitivity of the release means.

While only a particular embodiment of the present invention has been shown and described, it is apparent that changes and modifications may be made without departing from this invention in its broader aspects; and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

What is claimed is:

1. Apparatus adapted for plugging a well bore an comprising:

an upper body adapted to be suspended in a well bore;

a lower body tandemly arranged in relation to said upper body;

means defining an enclosed chamber in at least one of said bodies adapted to contain an initially-fluent hardenable substance;

means cooperatively arranged on said lower body and including extendible support means adapted for extension outwardly from said lower body for carrying a fluent substance discharged from said enclosed chamber;

means cooperatively arranged for discharging a fluent substance from said enclosed chamber onto said support means and including a piston selectively movable within said enclosed chamber from an elevated position to a lower position; and means releasably intercoupling said bodies and including means on one of said bodies defining a first abutment surface, means on the other of said bodies and including a movable member having an opposing second abutment surface cooperatively arranged for lateral movement between a first position where said abutment surfaces are abutted in longitudinal alignment with one another for coupling said bodies together and a second position where said abutment surfaces are laterally separated for uncoupling said bodies, a latch member pivotally coupled to one of said bodies and adapted for pivotal movement longitudinally between a transversely-extended latching position for retaining said movable member from movement away from its said first position and a longitudinallydisplaced releasing position for freeing said movable member for movement to its said second position, and latch-actuating means cooperatively arranged between said latch member and said piston and adapted for pivoting .said latch member to its said releasing position only upon movement of said piston toward its said lower position.

2. The apparatus of claim 1 wherein said latchactuating means include means cooperatively arranged on said latch member for counteracting laterallydirected forces acting thereon-and tending to pivot said latch member toward its said releasing position before said piston has moved toward its said lower position.

3. The apparatus of claim 1 wherein said latchactuating means include first and second actuating members respectively mounted on said piston and said latch member and cooperatively arranged to be coengaged as said piston nears its said lower position, and first and second means on said first and second actuating members respectively and responsive upon their coengagement for pivoting said latch member toward its said releasing position as said piston reaches its said lower position.

4. The apparatus of claim 3 further including:

balancing means cooperatively arranged on said latch member for counteracting laterally-directed inertial forces acting in one direction on said sec ond actuating member and tending to pivot said latch member toward its said releasing position be fore said piston is moved toward its said lower position.

5. Apparatus adapted for plugging a well bore and comprising:

an upper body adapted for suspension in a well bore and having an enclosed chamber defined therein adapted to contain an initiallyfluent hardenable substance;

at lower body having its upper end adapted to be interfitted with the lower end of said upper body; means cooperatively arranged on said lower body and including extendible support means adapted to be extended outwardly from said lower body for carrying a fluent substance discharged from said enclosed chamber;

means cooperatively arranged for discharging a fluent substance from said enclosed chamber onto said support means and including a piston selectively movable within said enclosed chamber from an elevated position to a lower position;

means releasably intercoupling said bodies and including first and second longitudinally-disposed locking fingers coupled to the opposite sides of the interfitted end of one of said bodies and adapted for lateral movement between outwardly-extended and inwardly-contracted positions, means on said locking fingers defining outwardly-directed first abutment surfaces facing said interfitted end of said one body, means on the opposite sides of the interfitted end of the other of said bodies defining inwardly-directed second abutment surfaces facing said interfitted end of said other body and adapted to be abutted with said first abutment surfaces to prevent separation of said bodies only so long as said locking fingers are retained in their said outwardly-extending position, a latch member having a length selected to span the lateral distance separating said locking fingers, and means pivotally coupling one end of said latch member to said first locking finger for pivotal movement along a generally-longitudinal plane between a fingerlatching position where the other end of said latch member is adjacent to said second locking finger to retain said locking fingers in their said outwardlyextending positions and a finger-releasing position where said other end of said latch member is laterally displaced from said second locking finger to free said locking fingers for movement to their said inwardly-contracted positions; and

means adapted for selectively moving said latch member from its said finger-latching position to its said finger-releasing position and including first and second cam surfaces cooperatively arranged on said latch member and said piston respectively for pivoting said latch member to its fingerreleasing position upon movement of said piston toward its said lower position sufficient to coengage said first and second cam surfaces.

6. The apparatus of claim 5 wherein said locking fingers are on said upper body.

7. The apparatus of claim 5 wherein said fingerreleasing position of said latch member is above its said finger-latching position.

8. The apparatus of claim 5 wherein said locking fingers are on said upper body and said finger-releasing position of said latch member is above its said fingerlatching position; and further including;

an opening cooperatively arranged in said second locking finger for receiving said other end of said latch member upon pivotal movement thereof to its said finger-releasing position.

9. The apparatus of claim 5 wherein said first and second abutment surfaces are respectively inclined in relation to the longitudinal axes of said bodies.

10. The apparatus of claim 9 wherein the angle of inclination of said abutment surfaces is between about 30 and about 75 from said longitudinal axes.

11. Apparatus adapted for plugging a well bore and comprising:

upper and lower tandemly-interfitted bodies adapted for suspension in a well bore and having an enclosed chamber defined in at least said upper body for containing an initially-fluent hardenable substance; an expansible tubular bag mounted around said lower body and adapted for expansion into anchoring engagement with a well bore wall upon receiving a supply of a fluent substance discharged from said enclosed chamber; means cooperatively arranged for discharging a fluent substance into said expansible bag from said enclosed chamber and including a piston selectively movable therein from an elevated position to a lower position;

means releasably intercoupling the adjacent ends of said interfitted bodies and including a pair of laterally-flexible locking fingers dependently mounted on opposite sides of said upper body and extending into said lower body, means on said locking fingers respectively defining upwardly-facing outwardly-projecting first inclined shoulders, means on the interior of said lower body defining downwardly-facing inwardly-opening second inclined shoulders adapted to be coengaged by said first shoulders only so long as said locking fingers are retained against inwardly-directed lateral movement from a body-locking position where said first and second shoulders are co-engaged to a body-releasing position where said first shoulders are laterally separated from said second shoulders, a latch member having a length selected to substantially span the lateral distance separating opposed inwardly-facing surfaces on said locking fingers, and means pivotally coupling one end of said latch member to one of opposed surfaces for pivotal movement along a generally-longitudinal plane between a finger-latching position where the other end of said latch member is movably engaged with the other of said opposed surfaces and a fingerreleasing position where said other latch end is longitudinally displaced from said other opposed surface sufficiently to free said locking fingers for inward movement to their said'body-releasing position; and

actuating means adapted for pivoting said latch member from its said finger-latching position to its said finger-releasing position in response to the discharge of a fluent substance from said enclosed chamber into said expansible bag.

12. The apparatus of claim 11 wherein said actuating means include:

a first cam member dependently mounted on said piston and including a downwardly-facing inclined cam surface, and a second cam member mounted in an upright position on said latch member and including an upwardly-facing inclined cam surface adapted to be contacted by said first cam surface as said piston approaches.

13. The apparatus of claim 12 further including means on said second cam member cooperatively arranged for minimizing inertial forces acting on said second cam member and tending to pivot said latch member to its said finger-releasing position.

14. The apparatus of claim 11 wherein said fingerreleasing position of said latch member is above its said finger-latching position; and further including:

means on said other opposed surface defining an opening adapted to receive said other end of said latch member whenever said latch member is pivoted to its said finger-releasing position.

15. The apparatus of claim 14 wherein said actuating means include:

a first actuating member mounted in a generallyupright position on said latch member and cooperatively arranged to engage the upper portion of said first actuating member with said other opposed surface above said opening when said latch member is in its said finger-latching position so that downwardly-directed inertial forces acting on said latch member will not pivot said latch member downwardly from its said finger latching position; a second actuating member dependently coupled to said piston and adapted to engage said first actuating member as said piston approaches its said lower position; an upwardly-facing camming surface on said upper portion of said first actuating member inclined upwardly and away from the point of engagement of said upper portion with said other opposed surface; and a downwardly-facing inclined camming surface on said second actuating member substantially complemental to said upwardly-facing camming surface and cooperatively arranged for progressively tilting said first actuating member away from said other opposed surface as said piston approaches its said lower position to pivot said latch member from its said finger-latching position to its said fingerreleasing position.

16. The apparatus of claim 15 further including:

means cooperatively arranged on said first'actuating member for minimizing inertial forces acting thereon and tending to pivot said latch member upwardly to its said finger-releasing position.

17. The apparatus of claim 15 further including:

means cooperatively arranged on said first actuating member for minimizing inertial forces acting thereon and tending to pivot said latch member upwardly to its said finger-releasing position; and

spring means normally biasing said latch member downwardly toward its said finger-latching positlon.

Claims

1. Apparatus adapted for plugging a well bore and comprising: an upper body adapted to be suspended in a well bore; a lower body tandemly arranged in relation to said upper body; means defining an enclosed chamber in at least one of said bodies adapted to contain an initially-fluent hardenable substance; means cooperatively arranged on said lower body and including extendible support means adapted for extension outwardly from said lower body for carrying a fluent substance discharged from said enclosed chamber; means cooperatively arranged for discharging a fluent substance from said enclosed chamber onto said support means and including a piston selectively movable within said enclosed chamber from an elevated position to a lower position; and means releasably intercoupling said bodies and including means on one of said bodies defining a first abutment surface, means on the other of said bodies and including a movable member having an opposing second abutment surface cooperatively arranged for lateral movement between a first position where said abutment surfaces are abutted in longitudinal alignment with one another for coupling said bodies together and a second position where said abutment surfaces are laterally separated for uncoupling said bodies, a latch member pivotally coupled to one of said bodies and adapted for pivotal movement longitudinally between a transversely-extended latching position for retaining said movable member from movement away from its said first position and a longitudinally-displaced releasing position for freeing said movable member for movement to its said second position, and latch-actuating means cooperatively arranged between said latch member and said piston and adapted for pivoting said latch member to its said releasing position only upon movement of said piston toward its said lower position.

2. The apparatus of claim 1 wherein said latch-actuating means include means cooperatively arranged on said latch member for counteracting laterally-directed forces acting thereon and tending to pivot said latch member toward its said rEleasing position before said piston has moved toward its said lower position.

3. The apparatus of claim 1 wherein said latch-actuating means include first and second actuating members respectively mounted on said piston and said latch member and cooperatively arranged to be coengaged as said piston nears its said lower position, and first and second means on said first and second actuating members respectively and responsive upon their coengagement for pivoting said latch member toward its said releasing position as said piston reaches its said lower position.

4. The apparatus of claim 3 further including: balancing means cooperatively arranged on said latch member for counteracting laterally-directed inertial forces acting in one direction on said second actuating member and tending to pivot said latch member toward its said releasing position before said piston is moved toward its said lower position.

5. Apparatus adapted for plugging a well bore and comprising: an upper body adapted for suspension in a well bore and having an enclosed chamber defined therein adapted to contain an initially-fluent hardenable substance; a lower body having its upper end adapted to be interfitted with the lower end of said upper body; means cooperatively arranged on said lower body and including extendible support means adapted to be extended outwardly from said lower body for carrying a fluent substance discharged from said enclosed chamber; means cooperatively arranged for discharging a fluent substance from said enclosed chamber onto said support means and including a piston selectively movable within said enclosed chamber from an elevated position to a lower position; means releasably intercoupling said bodies and including first and second longitudinally-disposed locking fingers coupled to the opposite sides of the interfitted end of one of said bodies and adapted for lateral movement between outwardly-extended and inwardly-contracted positions, means on said locking fingers defining outwardly-directed first abutment surfaces facing said interfitted end of said one body, means on the opposite sides of the interfitted end of the other of said bodies defining inwardly-directed second abutment surfaces facing said interfitted end of said other body and adapted to be abutted with said first abutment surfaces to prevent separation of said bodies only so long as said locking fingers are retained in their said outwardly-extending position, a latch member having a length selected to span the lateral distance separating said locking fingers, and means pivotally coupling one end of said latch member to said first locking finger for pivotal movement along a generally-longitudinal plane between a finger-latching position where the other end of said latch member is adjacent to said second locking finger to retain said locking fingers in their said outwardly-extending positions and a finger-releasing position where said other end of said latch member is laterally displaced from said second locking finger to free said locking fingers for movement to their said inwardly-contracted positions; and means adapted for selectively moving said latch member from its said finger-latching position to its said finger-releasing position and including first and second cam surfaces cooperatively arranged on said latch member and said piston respectively for pivoting said latch member to its finger-releasing position upon movement of said piston toward its said lower position sufficient to coengage said first and second cam surfaces.

7. The apparatus of claim 5 wherein said finger-releasing position of said latch member is above its said finger-latching position.

8. The apparatus of claim 5 wherein said locking fingers are on said upper body and said finger-releasing position of said latch member is above its said finger-latching position; and further including; an opening cooperatively arranged in said second locking finger for receiving said other end of said latch member upon pivotal movement thereof to its said finger-releasing position.

10. The apparatus of claim 9 wherein the angle of inclination of said abutment surfaces is between about 30* and about 75* from said longitudinal axes.

11. Apparatus adapted for plugging a well bore and comprising: upper and lower tandemly-interfitted bodies adapted for suspension in a well bore and having an enclosed chamber defined in at least said upper body for containing an initially-fluent hardenable substance; an expansible tubular bag mounted around said lower body and adapted for expansion into anchoring engagement with a well bore wall upon receiving a supply of a fluent substance discharged from said enclosed chamber; means cooperatively arranged for discharging a fluent substance into said expansible bag from said enclosed chamber and including a piston selectively movable therein from an elevated position to a lower position; means releasably intercoupling the adjacent ends of said interfitted bodies and including a pair of laterally-flexible locking fingers dependently mounted on opposite sides of said upper body and extending into said lower body, means on said locking fingers respectively defining upwardly-facing outwardly-projecting first inclined shoulders, means on the interior of said lower body defining downwardly-facing inwardly-opening second inclined shoulders adapted to be coengaged by said first shoulders only so long as said locking fingers are retained against inwardly-directed lateral movement from a body-locking position where said first and second shoulders are co-engaged to a body-releasing position where said first shoulders are laterally separated from said second shoulders, a latch member having a length selected to substantially span the lateral distance separating opposed inwardly-facing surfaces on said locking fingers, and means pivotally coupling one end of said latch member to one of opposed surfaces for pivotal movement along a generally-longitudinal plane between a finger-latching position where the other end of said latch member is movably engaged with the other of said opposed surfaces and a finger-releasing position where said other latch end is longitudinally displaced from said other opposed surface sufficiently to free said locking fingers for inward movement to their said body-releasing position; and actuating means adapted for pivoting said latch member from its said finger-latching position to its said finger-releasing position in response to the discharge of a fluent substance from said enclosed chamber into said expansible bag.

12. The apparatus of claim 11 wherein said actuating means include: a first cam member dependently mounted on said piston and including a downwardly-facing inclined cam surface, and a second cam member mounted in an upright position on said latch member and including an upwardly-facing inclined cam surface adapted to be contacted by said first cam surface as said piston approaches.

14. The apparatus of claim 11 wherein said finger-releasing position of said latch member is above its said finger-latching position; and further including: means on said other opposed surface defining an opening adapted to receive said other end of said latch member whenever said latch member is pivoted to its said finger-releasing position.

15. The apparatus of claim 14 wherein said actuating means include: a first actuating member mounted in a generally-upright positiOn on said latch member and cooperatively arranged to engage the upper portion of said first actuating member with said other opposed surface above said opening when said latch member is in its said finger-latching position so that downwardly-directed inertial forces acting on said latch member will not pivot said latch member downwardly from its said finger latching position; a second actuating member dependently coupled to said piston and adapted to engage said first actuating member as said piston approaches its said lower position; an upwardly-facing camming surface on said upper portion of said first actuating member inclined upwardly and away from the point of engagement of said upper portion with said other opposed surface; and a downwardly-facing inclined camming surface on said second actuating member substantially complemental to said upwardly-facing camming surface and cooperatively arranged for progressively tilting said first actuating member away from said other opposed surface as said piston approaches its said lower position to pivot said latch member from its said finger-latching position to its said finger-releasing position.

16. The apparatus of claim 15 further including: means cooperatively arranged on said first actuating member for minimizing inertial forces acting thereon and tending to pivot said latch member upwardly to its said finger-releasing position.

17. The apparatus of claim 15 further including: means cooperatively arranged on said first actuating member for minimizing inertial forces acting thereon and tending to pivot said latch member upwardly to its said finger-releasing position; and spring means normally biasing said latch member downwardly toward its said finger-latching position.